The High Speed Downlink Packet Access (HSDPA) is a technique proposed by the 3rd Generation Partnership Project (3GPP) in the Release-5 (Rel-5) and used to improve the network data throughput of the downlink direction (i.e. from network to terminal), and the downlink peak rate can be up to 14.4 Mbps.
In the physical layer, the HSDPA uses a High Speed-Physical Downlink Shared Channel (HS-PDSCH) in the downlink direction to bear the data of a High Speed-Downlink Shared Channel (HS-DSCH). Meanwhile, the HSDPA also uses a High Speed-Shared Control Channel (HS-SCCH) in the downlink direction to send before sending on the corresponding HS-PDSCH, to inform a User Equipment (UE) of some necessary information of the HS-PDSCH sent after the HS-SCCH, and the information includes used spread spectrum code, modulation scheme, transmission block size, Hybrid Automatic Repeat Request (HARQ) process, redundancy version, new data indication and UE identifier, thus the UE specified by the UE identifier can correctly receive the sent data, and the other UEs can not correctly receive the data. In the uplink direction, the HSDPA uses a High Speed Dedicated Physical Control Channel (HS-DPCCH) of the HS-DSCH. The UE feeds back whether a transmission block of the HS-DSCH is correctly received to the network via the HS-DPCCH, wherein an ACK in the fed back information means that the transmission block is correctly received and NACK means that the transmission block is not correctly received, if the transmission block is not correctly received, the data need to be retransmitted. Meanwhile, the UE also feeds back a Channel Quality Indicator (CQI). A CQI table is pre-defined, and each CQI value corresponds to a fixed transmission block size, an HS-PDSCH number and an HS-DSCH subframe of the modulation scheme. The UE should feed back a maximum CQI, which represents that if the HS-DSCH subframe corresponding to the CQI is received by the UE one time slot before a HS-DPCCH subframe carrying the CQI is sent, the error probability of the corresponding transmission block is less than 10%, and this is served as a reference for the radio channel quality of the UE.
In the design of HS-DPCCH, 10 bits of data are used to bear the HARQ-ACK information, furthermore, 20 bits are used to bear the CQI information. Each UE belongs to a specific UE Category according to different capacities, the CQI table corresponding to the UE has 31 items in total, and can be represented by 5-bit data and coded with 20 bits to map to the CQI bit field of the HS-DPCCH. HARQ has two kinds of situations, namely, ACK and NACK, which respectively represent that the data block is correctly received and the received data block has an error, and the HARQ is coded with 10 bits through a specific code book to map to the HARQ-ACK bit field of the HS-DPCCH.
In the following, the 3GPP is strengthened from multiple aspects on the basis of the HSDPA. The Multiple Input Multiple Output (MIMO) antenna technique is a way for improving the radio channel transmission bandwidth therein. The 3GPP adopts the MIMO technique in the Rel-7, which permits that at most two transmission blocks (a main transmission block and an auxiliary transmission block) are simultaneously transmitted to the same UE in a Transmission Time Interval (TTI) of 2 ms. To support the MIMO technique, a sending party needs to modulate the data onto two noncoherent antennas to be simultaneously sent, a receiving party also needs to simultaneously receive the data from the two noncoherent antennas and performs demodulation. In common with the HSDPA, the UE also needs to feed back the HARQ-ACK and CQI after receiving the HS-DSCH data. The difference is that the UE needs to respectively feed back the HARQ-ACK to the two simultaneously received HS-DSCH transmission blocks, and the CQI also corresponds to two space division channels and is recorded as CQI1 and CQI2. In addition, the UE also needs to feed back an antenna array weight namely a precoding weight required by a closed loop MIMO, so as to make the transmission block size maximize. There are four precoding weights: w1, w2, w3 and w4, the (w1, w2) constitute a main precoding vector to perform weighting on the data of the main transmission block; the (w3, w4) constitute an auxiliary precoding vector to perform weighting on the data of the auxiliary transmission block. The main precoding vector is used to transmit the main transmission block and the auxiliary precoding vector is used to transmit the auxiliary transmission block. In the four precoding weights, w1 and w3 are fixed values, w2 and w4 have a fixed symbol relationship, and thus, the UE only needs to feed back the precoding weight w2, which is implemented through a Pre-coding Indicator (PCI). The w2 can take one of the four values, thus the PCI is 2-bit data. In the condition of MIMO, a new CQI table is used, the CQI table corresponding to each specific UE Category has 15 items and is represented by 4-bit data, and the CQI1/CQI2 needs 8 bits in total. Therefore, a combination of PCI/CQI is 10-bit data, and is coded with 20 bits to map to the CQI/PCI bit field (i.e. the original CQI bit field) of the HS-DPCCH. HARQ is required to consider 6 kinds of situations of the combination of ACK/NACK in the condition of single stream and dual stream, and is coded with 10 bits through the specific code book to map to the HARQ-ACK bit field of the HS-DPCCH.
The MIMO technique improves the bandwidth by simultaneously increasing the number of antennas at the sending party and receiving party. If the MIMO technique is not adopted, the bandwidth also can be improved by increasing the number of carriers. To improve the downlink bandwidth further, the 3GPP introduces a Dual Cell-HSDPA (DC-HSDPA) technique in the Rel-8 and uses two adjacent carriers (a main carrier and an auxiliary carrier) to improve the downlink bandwidth. The main carrier and auxiliary carrier respectively configure the HS-PDSCH and HS-SCCH at the same time and perform independent scheduling. For the UE with the ability of receiving the DC-HSDPA, the HSDPA data can be simultaneously received on the main carrier and auxiliary carrier. In common with a single carrier HSDPA, the UE also needs to feed back the HARQ-ACK and CQI after receiving the HS-DSCH data; the difference is that the UE needs to respectively feed back the HARQ-ACK to two HS-DSCH transmission blocks simultaneously received over two carriers, and the CQI also corresponds to the two carriers and is recorded as CQI1 and CQI2. The CQI table corresponding to each CQI has 31 items in total and is represented by 5-bit data, the CQI1 and CQI2 have 10-bit data in total, and are coded with 20 bits to map to the CQI bit field of the HS-DPCCH. HARQ needs to consider 8 kinds of situations of the combination of ACK and NACK in the condition of single carrier and multi-carrier system, and is coded with 10 bits through the specific code book to map to the HARQ-ACK bit field of the HS-DPCCH.
To further improve the downlink bandwidth, the 3GPP combines the DC-HSDPA and MIMO in the Rel-9. In the design of HS-DPCCH, considering the performance and power consumption comprehensively, one HS-DPCCH is still adopted for information feedback. HARQ needs to consider 48 kinds of situations of the combination of ACK and NACK in the conditions of the main carrier and auxiliary carrier and the single stream and dual stream, and is coded with 10 bits through the specific code book to map to the HARQ-ACK bit field of the HS-DPCCH. The PCI needs to perform feedback for the main carrier and auxiliary carrier respectively, is recorded as PCI1 and PCI2 respectively, which are 4-bit data in total. For the CQI, it is defined by using the MIMO CQI table in the Rel-7, each carrier has the CQI1/CQI2 which is 8-bit data, and the main carrier and auxiliary carrier are 16-bit data in total. In other words, the CQI/PCI of the main carrier is 10-bit data and the CQI/PCI of the auxiliary carrier is also 10-bit data. In HS-DPCCH transmission, the CQI/PCI of the main carrier is 10-bit data in total, and is coded with 20 bits to map to the CQI/PCI bit field of one subframe of two successive subframes of the HS-DPCCH; the CQI/PCI of the auxiliary carrier is 10-bit data in total, and is coded with 20 bits to map to the CQI/PCI bit field of another subframe of the two successive subframes of the HS-DPCCH. That is, the CQI/PCI data of the main carrier and auxiliary carrier are transmitted on the HS-DPCCH by the way of time-division multiplexing.
To further improve the user peak rate, more carriers require to be combined and transmitted. For example, if MIMO data are transmitted over a bandwidth of 20 MHz, it requires up to 4 carriers (called as 4C in the following) to be combined, and each carrier can support the HSDPA and MIMO. HARQ information required to be fed back by each carrier is one of the A/N/D/AA/AN/NA/NN and has 7 kinds of situations in total. According to the existing method for transmitting HARQ feedback information, the number of combinations required to be considered in the condition of 4C is 7×7×7×7−1=2400. Because the data field bearing the HARQ feedback information is of 10 bits, 1024 kinds of situations can be fed back at most, and the feedback demand of the HARQ information has been far beyond the bearing capacity of the 10-bit data field. Therefore, a new method for transmitting HARQ information is required and can satisfy the transmission requirement of the HARQ information in the condition of the 4C HSDPA combining with MIMO. Two choices for the HS-DPCCH are discussed in the 3GPP conference, one is to adopt one HS-DPCCH with a spreading factor of 128; the other is to adopt two HS-DPCCHs with a spreading factor still being 256. But no matter which way is adopted, when the multiple carriers such as 3 carriers or 4 carriers are supported, the HS-DPCCH will inevitably change, and the existing technology does not have a method for triggering a Radio Network Controller (RNC) to update resources.